FRUIT-FEEDING BEHAVIOR OF BANDED FRUIT WEEVIL, PHLYCTINUS-CALLOSUS (SCHONHERR) (COL, CURCULIONIDAE), IN APPLE ORCHARDS

The seasonal fruit-feeding behaviour of adults of Phlyctinus callosus in Granny Smith apple orchards, and the extent of the resultant crop loss was monitored on two farms during a number of successive seasons. Fruit feeding started at fruit set and reached maximum levels within 6 weeks. Thereafter, it abruptly decreased, even though there were still some 10 weeks to harvest. Evidence indicates that the sudden decrease in fruit-feeding is due to a reduction in the functional value of adult mandibles caused by feeding. Renewed periods of fruit feeding on a smaller scale sometimes occurred in mid-season and shortly before harvest. These periods were closely related to periods of increased adult emergence. The dispersion pattern in the trees of fruit damaged by P. callosus was contagious, indicating aggregation behaviour during feeding by this species. The crop loss in apple orchards due to uncontrolled populations of P. callosus was very variable. Fruit damage between trees varied from less than 1 % to 66 %, and mean crop loss between seasons from 5 % to 29 %. Between 70 % and 99 % of fruit damage was caused during the first 3 months after fruit set. The implications of fruit feeding behaviour for the economic management of P. callosus are briefly discussed.